Technology disclosed in JP 2013-99071A, for example, is known as conventional technology for dissipating heat generated by electronic components in a circuit structure in a vehicle-mounted electrical component or the like. JP 2013-99071A discloses technology in which heat generated by electronic components is transferred to a heat sink (heat dissipating member) via a bus bar and an insulating heat transfer member and is dissipated from the heat sink. At this time, a thermosetting adhesive is conventionally used as the insulating heat transfer member. Also, in order to omit steps required for thermosetting, which involves increasing the temperature for heating and time for cooling, there are also cases where a room temperature setting adhesive is used instead of the thermosetting adhesive.
However, if a room temperature setting adhesive is used as the insulating heat transfer member, the hardness of the room temperature setting adhesive is normally less than the thermosetting adhesive, and thus the room temperature setting adhesive disposed between a bus bar and a heat dissipating member may escape to the surrounding region due to stress generated by cooling and heating cycles in the atmospheric temperature. That is to say, if the room temperature setting adhesive softens when the atmospheric temperature is high, the room temperature setting adhesive between a highly rigid bus bar and a heat dissipating member will be pushed out into the surrounding region. In this case, when the atmospheric temperature decreases, the amount of room temperature setting adhesive directly below an electronic component that is a heat-generating element may be insufficient. Accordingly, for example, there is concern of the boundary surfaces between the bus bar and the heat dissipating member coming apart. If the boundary surfaces between the bus bar and the heat dissipating member come apart, the heat transferred from the bus bar to the heat transferring member decreases, and thus the heat dissipation effect exhibited by the heat dissipating member is reduced.
Thus, it is conceivable to provide a restriction member for restricting such a room temperature setting adhesive from being pushed out into the surrounding region when the temperature is high. However, the restricting member is also affected by stress, which is caused by cooling and heating cycles in the atmospheric temperature, acting on the insulating heat transfer member, and it is conceivable that, when the amount of stress is high, the insulating heat transfer member may come out from the restricting member.
The technology disclosed in the present specification was completed based on circumstances such as those described above, and the present specification provides a circuit structure that can suppress a reduction in the heat dissipating effect exhibited by the heat dissipating member, even if a restriction member that restricts movement of the insulating heat transfer member caused by an increase in temperature is provided.